My bugbear is that, having taught calculus, problems like these confuse students by apparently validating intuitional misconceptions. It’s the sort of problem you give to your star students with the express instruction to identify the flaw.

I found it on Quora, where someone posted it in answer to the question "What are some math problems you can confront your grade 10 teacher with?"

I found it on Quora, where someone posted it in answer to the question "What are some math problems you can confront your grade 10 teacher with?"

Okay, in that situation I would spend a few minutes describing to the students in detail how and why the misconception is faulty, and say that it illustrates the great importance of being careful how mathematical constructs are formulated.